Re: Counterquestion - is Oracle a He or a She - or an It or a hermaphrodite

Comments below
On 8/6/05, Kennedy, Jim <jim_kennedy@xxxxxxxxxx> wrote: 
> 
> 
> 
> I explain NULLS in the following manner.
> 
> Imagine a medical application where your medical data is stored in a
> database. Imagine that your Dr. has never asked you if you have
> allergies or not. Further imagine that you become unconcouse and go to
> the emergency room. The Dr. in the emergency room looks at your
> electronic medical data. Given the information in your electronic chart
> what should the Dr. assume about your allergic reactions?:
> A. You are Alergic to something.
> B. You are not allergic to anything.
> C. It is unknown if you are or are not allergic to anything.
> 
> The Dr. should assume C. You have not been asked the question so the
> data in that column is NULL and the Dr. should make NO assumptions about
> your medical condition visa vis allergys. In medicine even if they
> asked you the question "Are you allergic to anything?" and you answered
> "No" the correct value to store is NKA - No Known Allergies. After
> this explanation most people understand what a NULL is.
> Jim

 Isn't this a great example of how a better design is a better solution? 
Wouldn't 
 PATIENT
=======
PATIENT_PK
....................
 ALLERGEN
=========
ALLERGEN_PK
........................
 KNOWN_ALLERGIES
================
PATIENT_PK -- foreign key
ALLERGEN_PK -- foreign key
IDENTIFIED_DATE
.....

Be a better design? Then the doctor would just pull up a list of known 
allergies (which might of course be empty). This is a lot different, and I'd 
argue better, than pulling up a NKA or NULL value. 

-- 
Niall Litchfield
Oracle DBA
http://www.niall.litchfield.dial.pipex.com

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